Use KahanSum to compute RMSE.

Fix typos.

src/nvtt/tests/stress.cpp

@@ -26,6 +26,7 @@
 #include <nvimage/ImageIO.h>
 #include <nvimage/BlockDXT.h>
 #include <nvimage/ColorBlock.h>
+#include <nvmath/KahanSum.h>
 #include <nvcore/Ptr.h>
 #include <nvcore/Debug.h>
 #include <nvcore/StrLib.h>
@@ -166,7 +167,7 @@ float rmsError(const Image * a, const Image * b)
 	nvCheck(a->width() == b->width());
 	nvCheck(a->height() == b->height());
 
-	float mse = 0;
+	KahanSum mse;
 
 	const uint count = a->width() * a->height();
 
@@ -180,14 +181,12 @@ float rmsError(const Image * a, const Image * b)
 		int b = c0.b - c1.b;
 		//int a = c0.a - c1.a;
 
-		mse += r * r;
-		mse += g * g;
-		mse += b * b;
+		mse.add(r * r);
+		mse.add(g * g);
+		mse.add(b * b);
 	}
 
-	mse /= count;
-
-	return sqrtf(mse);
+	return sqrtf(mse.sum() / count);
 }
 
 
@@ -277,7 +276,7 @@ int main(int argc, char *argv[])
 	TextWriter csvWriter(&csvStream);
 
 	float totalTime = 0;
-	float totalRMS = 0;
+	float totalRMSE = 0;
 	int failedTests = 0;
 	float totalDiff = 0;
 
@@ -314,13 +313,13 @@ int main(int argc, char *argv[])
 			printf("Error saving file '%s'.\n", outputFileName.str());
 		}
 
-		float rms = rmsError(img.ptr(), img_out.ptr());
-		totalRMS += rms;
+		float rmse = rmsError(img.ptr(), img_out.ptr());
+		totalRMSE += rmse;
 
-		printf("  RMS:  \t%.4f\n", rms);
+		printf("  RMSE:  \t%.4f\n", rmse);
 
 		// Output csv file
-		csvWriter << "\"" << s_fileNames[i] << "\"," << rms << "\n";
+		csvWriter << "\"" << s_fileNames[i] << "\"," << rmse << "\n";
 
 		if (regressPath != NULL)
 		{
@@ -335,9 +334,9 @@ int main(int argc, char *argv[])
 				return EXIT_FAILURE;
 			}
 
-			float rms_reg = rmsError(img.ptr(), img_reg.ptr());
+			float rmse_reg = rmsError(img.ptr(), img_reg.ptr());
 
-			float diff = rms_reg - rms;
+			float diff = rmse_reg - rmse;
 			totalDiff += diff;
 
 			const char * text = "PASSED";
@@ -353,12 +352,12 @@ int main(int argc, char *argv[])
 		fflush(stdout);
 	}
 
-	totalRMS /= s_fileCount;
+	totalRMSE /= s_fileCount;
 	totalDiff /= s_fileCount;
 
 	printf("Total Results:\n");
 	printf("  Total Time: \t%.3f sec\n", totalTime / CLOCKS_PER_SEC);
-	printf("  Average RMS:\t%.4f\n", totalRMS);
+	printf("  Average RMSE:\t%.4f\n", totalRMSE);
 
 	if (regressPath != NULL)
 	{